Re: [LTP] [PATCH] Synchronization between two processes

["Serge E. Hallyn" <serue@us.ibm.com>]

Quoting Subrata Modak (subrata@linux.vnet.ibm.com):
> On Fri, 2009-05-15 at 08:45 -0500, Serge E. Hallyn wrote: 
> > Quoting Gui Xiaohua (guixh@cn.fujitsu.com):
> > > The child-process wait SIGUSR1 which would be sended by parent-process,
> > > if the child-process execute sigtimedwait() after parent-process send 
> > > the signal, it would never receive the SIGUSR1 from parent-process.
> > > I cann't make sure the SIGUSR1 be sended after child-process execute 
> > > sigtimedwait() with 100 percent, and i try my best.
> > 
> > Well, in theory I suppose this could happen, but you'd have to have
> > a pretty bad scheduler if the parent can do a strcmp(buf, "c:go")
> > between the pipe read and signal send, while the child goes straight
> > from pipe write to sigtimedwait.
> > 
> > Have you seen this signal be missed?  If not, then I'd rather assume
> > things are reasonable.  If you have seen this happen, then why not
> > instead set up a SIGUSR1 handler in the child before doing the pipe
> > write, then just sleep for 3 seconds instead of doing sigtimedwait?
> 
> Thanks Serge.

Or, if I'm being unreasonable, then at least have the parent only wait
for at most 1 second, and leave the child alone.  Every every ltp test
is going to hang for 5 seconds...

But I prefer setting the signal handler ahead of time.

> Gui,
> 
> Are you planning any further patch(s) for this ?

thanks,
-serge

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